The present invention relates generally to muscle exercise and rehabilitation apparatus, and more particularly, is directed to such apparatus for exercise and rehabilitation of the upper lumbar region of the back.
The vertebral column is a complex structure which is designed to support loads, protect the spinal cord, and attenuate the forces that are commonly transferred to and from the trunk and arms to the lower extremities. Although structurally quite strong, the trunk is subjected to such large forces during everyday tasks that it is presently estimated that 80 percent of the general U.S. population will at some time in their lives experience a low back disorder.
The vertebral column is functionally required to move and experience loads in three planes about three distinct axes. The sagittal plane divides the body into left and right halves. Trunk flexion and extension occur in this plane about a frontal axis which goes left to right. The coronal plane divides the body into anterior and posterior parts. Lateral flexion of the trunk occurs in this plane about the anteroposterior axis. The transverse plane divides the body into superior and anterior parts. Trunk rotation occurs in this plane about a vertical axis. The apparatus according to the present invention addresses trunk flexion and extension in the sagittal plane, as will be described in greater detail hereinafter.
As to the basic anatomy of the vertebral column, the vertebral column is made up of 24 true vertebrae, seven cervical, twelve thoracic, and five lumbar. There are five sacral vertebrae which in the adult are fused together, thereby not representing true vertebrae.
There are three major curves associated with the vertebral column which are functional in the support of the body. The curve of the lumbar region and the cervical curve are referred to as secondary since they are not present at birth as is the thoracic curve. The lumbar and cervical curves are convex anteriorly, whereas the thoracic curve is convex posteriorly. There are normal deviations from vertical in the coronal plane as well.
Each vertebra is separated from adjacent vertebrae by intervertebral discs. The discs function as shock absorbers between the vertebral bodies. There are two major components of discs, a viscous inner portion called the nucleus pulposis and a tough fibrous tissue surrounding the nucleus called the annulus fibrosis. Due to the forces that the vertebral column commonly experiences, the annulus will sometimes become herniated allowing the nucleus to seep out of confinement. The flow of the nucleus out of the annulus will often impinge upon spinal nerves causing clinical problems ranging from pain to quasiparalysis. This is commonly referred to as a "slipped disc."
The individual vertebrae and intervertebral discs are stabilized by the vertebral ligaments. The posterior ligaments are those which tend to resist the vertebral column's tendency to flex, and the anterior ligaments are those which help prevent extension. The ligaments are strong and somewhat inelastic. They represent what some people call the last line of defense against range of motion injury. However, these ligaments can become injured when stretched too far.
The musculature of the vertebral column is extensive and complex. A simple classification scheme is based upon their location. The anterior vertebral muscles are those which tend to cause vertebral flexion. This group includes the abdominal muscles (rectus abdominus, the external obliques, and the internal obliques.) The psoas major and minor muscles have attachments to the anterior aspect of the vertebral column in the lumbar region. Interestingly, these muscles have a tendency to cause extension of the lumbar vertebrae.
The primary extensors are those muscles which are classified as posterior vertebral muscles. A further simplification of the muscles places them in a single group of muscles called the erector spinae. As will be explained hereinafter, the apparatus of the present invention has as one of its fundamental purposes of the assessment of the functional capacity of the lumbar mechanism in the sagittal plane.
The loads on the vertebral column come from three sources: body weight, external forces, and internal forces. Any particular vertebrae will be affected by the weight of any body mass which is superior to its location. External forces comprise any force, or weight, that is added to the system, e.g., a backpack or an object held in the hands. Since the hands attach via the arms to the shoulders, a weight held in the hands subsequently affects all of the vertebrae which are inferior to the level of the shoulder joint.
Internal forces represent any forces that are created by muscles and ligaments. The erector spinae, for example, which are found bilaterally just lateral to the vertebral column, cause the vertebral column to undergo compressive forces when they contract.
There are three basic types of forces that affect the vertebral column. In general, these are compression, shear, and torsion forces. Compression forces act predominately upon the intervertebral discs. Shear forces, however, have their predominant effect at the intervertebral foramen, the site at which spinal nerves exit from the vertebral column. Torsion forces are twisting forces and may affect both of these structures.
Tension is a force quite common in the vertebral column. During flexion of the trunk, for example, the anterior aspect of the intervertebral body undergoes compression as a result of the adjacent vertebral bodies moving closer to one another. The posterior aspect of the intervertebral disc, however, undergoes tension, as do the posterior vertebral ligaments which serve to restrict the degree of flexion which may occur.
Now, with the above as background, a problem with conventional back exercise and rehabilitation apparatus is that during motion of the back, the support for the lumbar region changes. Therefore, with a fixed lumbar support, the patient may feel discomfort and optimum results may not be obtained.
In addition, with conventional back apparatus, lordosis which is the forward curvature of the spine, that produces a hollow in the back, is not maintained throughout the entire range of motion. This, again, can cause discomfort to the patient and failure to obtain optimum results. In other words, the lumbar region may in effect become isolated which puts a great amount of stress on the joints.
Further, conventional apparatus do not provide a cervical support that can be adjusted up and down for the entire antrhropomorphic range. Also, many such apparatus do not provide for control of substitution by the lower extremities, that is, protecting the lumbar spine by enabling some use of other muscles during exercise and rehabilitation.
U.S. Pat. No. 4,666,152 discloses a lower back exercising machine, in which the seat in the first embodiment is inclined upwardly toward the front thereof. In this first embodiment, there is no adjustable foot support assembly, lumbar pad, or cervical support. Although the padded roller could generally be termed a scapula pad, this pad is not adjustable. In the second embodiment, the person leans, but does not sit, on a padded seat. Although the seat is inclined downwardly toward the front thereof, the angle of inclination is approximately 50 degrees. This is because the person leans against the seat, rather than sitting on it. Also, although a padded roller is provided, which could be deemed a scapula roller, it is not adjustable with respect to the frame.
U.S. Pat. No. 4,565,368 discloses an isokinetic exercise machine for the back muscles. However, this patent fails to cure the deficiencies of U.S. Pat. No. 4,666,152. There is no seat at all. Further, there is no adjustable foot support assembly, lumbar pad, scapula pad or cervical support in accordance with the teachings of the present invention.
Other patents which relate only peripherally, at most, to the present invention, are U.S. Pat. Nos. 3,641,995; 3,975,051; 4,215,680; and 4,669,724.